#include "libks/ks_utf8.h"

/*
  Basic UTF-8 manipulation routines
  by Jeff Bezanson
  placed in the public domain Fall 2005

  This code is designed to provide the utilities you need to manipulate
  UTF-8 as an internal string encoding. These functions do not perform the
  error checking normally needed when handling UTF-8 data, so if you happen
  to be from the Unicode Consortium you will want to flay me alive.
  I do this because error checking can be performed at the boundaries (I/O),
  with these routines reserved for higher performance on data known to be
  valid.
*/

static const uint32_t offsetsFromUTF8[6] = {
    0x00000000UL, 0x00003080UL, 0x000E2080UL,
    0x03C82080UL, 0xFA082080UL, 0x82082080UL
};

static const char trailingBytesForUTF8[256] = {
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
    2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, 3,3,3,3,3,3,3,3,4,4,4,4,5,5,5,5
};

/* returns length of next utf-8 sequence */
KS_DECLARE(int) ks_u8_seqlen(char *s)
{
	return trailingBytesForUTF8[(unsigned int)(unsigned char)s[0]] + 1;
}

/* conversions without error checking
   only works for valid UTF-8, i.e. no 5- or 6-byte sequences
   srcsz = source size in bytes, or -1 if 0-terminated
   sz = dest size in # of wide characters

   returns # characters converted
   dest will always be L'\0'-terminated, even if there isn't enough room
   for all the characters.
   if sz = srcsz+1 (i.e. 4*srcsz+4 bytes), there will always be enough space.
   */
KS_DECLARE(int) ks_u8_toucs(uint32_t *dest, int sz, char *src, int srcsz)
{
	uint32_t ch;
	char *src_end = src + srcsz;
	int nb;
	int i=0;

	while (i < sz-1) {
		nb = trailingBytesForUTF8[(unsigned char)*src];
		if (srcsz == -1) {
			if (*src == 0)
				goto done_toucs;
		}
		else {
			if (src + nb >= src_end)
				goto done_toucs;
		}
		ch = 0;
		switch (nb) {
			/* these fall through deliberately */
			case 3: ch += (unsigned char)*src++; ch <<= 6;
			case 2: ch += (unsigned char)*src++; ch <<= 6;
			case 1: ch += (unsigned char)*src++; ch <<= 6;
			case 0: ch += (unsigned char)*src++;
		}
		ch -= offsetsFromUTF8[nb];
		dest[i++] = ch;
	}
done_toucs:
	dest[i] = 0;
	return i;
}

/* srcsz = number of source characters, or -1 if 0-terminated
   sz = size of dest buffer in bytes

   returns # characters converted
   dest will only be '\0'-terminated if there is enough space. this is
   for consistency; imagine there are 2 bytes of space left, but the next
   character requires 3 bytes. in this case we could NUL-terminate, but in
   general we can't when there's insufficient space. therefore this function
   only NUL-terminates if all the characters fit, and there's space for
   the NUL as well.
   the destination string will never be bigger than the source string.
   */
KS_DECLARE(int) ks_u8_toutf8(char *dest, int sz, uint32_t *src, int srcsz)
{
	uint32_t ch;
	int i = 0;
	char *dest_end = dest + sz;

	while (srcsz<0 ? src[i]!=0 : i < srcsz) {
		ch = src[i];
		if (ch < 0x80) {
			if (dest >= dest_end)
				return i;
			*dest++ = (char)ch;
		}
		else if (ch < 0x800) {
			if (dest >= dest_end-1)
				return i;
			*dest++ = (char)((ch>>6) | 0xC0);
			*dest++ = (ch & 0x3F) | 0x80;
		}
		else if (ch < 0x10000) {
			if (dest >= dest_end-2)
				return i;
			*dest++ = (char)((ch>>12) | 0xE0);
			*dest++ = ((ch>>6) & 0x3F) | 0x80;
			*dest++ = (ch & 0x3F) | 0x80;
		}
		else if (ch < 0x110000) {
			if (dest >= dest_end-3)
				return i;
			*dest++ = (char)((ch>>18) | 0xF0);
			*dest++ = ((ch>>12) & 0x3F) | 0x80;
			*dest++ = ((ch>>6) & 0x3F) | 0x80;
			*dest++ = (ch & 0x3F) | 0x80;
		}
		i++;
	}
	if (dest < dest_end)
		*dest = '\0';
	return i;
}

KS_DECLARE(int) ks_u8_wc_toutf8(char *dest, uint32_t ch)
{
	if (ch < 0x80) {
		dest[0] = (char)ch;
		return 1;
	}
	if (ch < 0x800) {
		dest[0] = (char)((ch>>6) | 0xC0);
		dest[1] = (ch & 0x3F) | 0x80;
		return 2;
	}
	if (ch < 0x10000) {
		dest[0] = (char)((ch>>12) | 0xE0);
		dest[1] = ((ch>>6) & 0x3F) | 0x80;
		dest[2] = (ch & 0x3F) | 0x80;
		return 3;
	}
	if (ch < 0x110000) {
		dest[0] = (char)((ch>>18) | 0xF0);
		dest[1] = ((ch>>12) & 0x3F) | 0x80;
		dest[2] = ((ch>>6) & 0x3F) | 0x80;
		dest[3] = (ch & 0x3F) | 0x80;
		return 4;
	}
	return 0;
}

/* charnum => byte offset */
KS_DECLARE(int) ks_u8_offset(char *str, int charnum)
{
	int offs=0;

	while (charnum > 0 && str[offs]) {
		(void)(isutf(str[++offs]) || isutf(str[++offs]) ||
				isutf(str[++offs]) || ++offs);
		charnum--;
	}
	return offs;
}

/* byte offset => charnum */
KS_DECLARE(int) ks_u8_charnum(char *s, int offset)
{
	int charnum = 0, offs=0;

	while (offs < offset && s[offs]) {
		(void)(isutf(s[++offs]) || isutf(s[++offs]) ||
				isutf(s[++offs]) || ++offs);
		charnum++;
	}
	return charnum;
}

/* number of characters */
KS_DECLARE(int) ks_u8_strlen(char *s)
{
	int count = 0;
	int i = 0;

	while (ks_u8_nextchar(s, &i) != 0)
		count++;

	return count;
}

/* reads the next utf-8 sequence out of a string, updating an index */
KS_DECLARE(uint32_t) ks_u8_nextchar(char *s, int *i)
{
	uint32_t ch = 0;
	int sz = 0;

	do {
		ch <<= 6;
		ch += (unsigned char)s[(*i)++];
		sz++;
	} while (s[*i] && !isutf(s[*i]));
	ch -= offsetsFromUTF8[sz-1];

	return ch;
}

KS_DECLARE(void) ks_u8_inc(char *s, int *i)
{
	(void)(isutf(s[++(*i)]) || isutf(s[++(*i)]) ||
			isutf(s[++(*i)]) || ++(*i));
}

KS_DECLARE(void) ks_u8_dec(char *s, int *i)
{
	(void)(isutf(s[--(*i)]) || isutf(s[--(*i)]) ||
			isutf(s[--(*i)]) || --(*i));
}

KS_DECLARE(int) octal_digit(char c)
{
	return (c >= '0' && c <= '7');
}

KS_DECLARE(int) hex_digit(char c)
{
	return ((c >= '0' && c <= '9') ||
			(c >= 'A' && c <= 'F') ||
			(c >= 'a' && c <= 'f'));
}

/* assumes that src points to the character after a backslash
   returns number of input characters processed */
KS_DECLARE(int) ks_u8_read_escape_sequence(char *str, uint32_t *dest)
{
	uint32_t ch;
	char digs[9]="\0\0\0\0\0\0\0\0";
	int dno=0, i=1;

	ch = (uint32_t)str[0];    /* take literal character */
	if (str[0] == 'n')
		ch = L'\n';
	else if (str[0] == 't')
		ch = L'\t';
	else if (str[0] == 'r')
		ch = L'\r';
	else if (str[0] == 'b')
		ch = L'\b';
	else if (str[0] == 'f')
		ch = L'\f';
	else if (str[0] == 'v')
		ch = L'\v';
	else if (str[0] == 'a')
		ch = L'\a';
	else if (octal_digit(str[0])) {
		i = 0;
		do {
			digs[dno++] = str[i++];
		} while (octal_digit(str[i]) && dno < 3);
		ch = strtol(digs, NULL, 8);
	}
	else if (str[0] == 'x') {
		while (hex_digit(str[i]) && dno < 2) {
			digs[dno++] = str[i++];
		}
		if (dno > 0)
			ch = strtol(digs, NULL, 16);
	}
	else if (str[0] == 'u') {
		while (hex_digit(str[i]) && dno < 4) {
			digs[dno++] = str[i++];
		}
		if (dno > 0)
			ch = strtol(digs, NULL, 16);
	}
	else if (str[0] == 'U') {
		while (hex_digit(str[i]) && dno < 8) {
			digs[dno++] = str[i++];
		}
		if (dno > 0)
			ch = strtol(digs, NULL, 16);
	}
	*dest = ch;

	return i;
}

/* convert a string with literal \uxxxx or \Uxxxxxxxx characters to UTF-8
example: u8_unescape(mybuf, 256, "hello\\u220e")
note the double backslash is needed if called on a C string literal */
KS_DECLARE(int) ks_u8_unescape(char *buf, int sz, char *src)
{
	int c=0, amt;
	uint32_t ch;
	char temp[4];

	while (*src && c < sz) {
		if (*src == '\\') {
			src++;
			amt = ks_u8_read_escape_sequence(src, &ch);
		}
		else {
			ch = (uint32_t)*src;
			amt = 1;
		}
		src += amt;
		amt = ks_u8_wc_toutf8(temp, ch);
		if (amt > sz-c)
			break;
		memcpy(&buf[c], temp, amt);
		c += amt;
	}
	if (c < sz)
		buf[c] = '\0';
	return c;
}

KS_DECLARE(int) ks_u8_escape_wchar(char *buf, int sz, uint32_t ch)
{
	if (ch == L'\n')
		return snprintf(buf, sz, "\\n");
	else if (ch == L'\t')
		return snprintf(buf, sz, "\\t");
	else if (ch == L'\r')
		return snprintf(buf, sz, "\\r");
	else if (ch == L'\b')
		return snprintf(buf, sz, "\\b");
	else if (ch == L'\f')
		return snprintf(buf, sz, "\\f");
	else if (ch == L'\v')
		return snprintf(buf, sz, "\\v");
	else if (ch == L'\a')
		return snprintf(buf, sz, "\\a");
	else if (ch == L'\\')
		return snprintf(buf, sz, "\\\\");
	else if (ch < 32 || ch == 0x7f)
		return snprintf(buf, sz, "\\x%hhX", (unsigned char)ch);
	else if (ch > 0xFFFF)
		return snprintf(buf, sz, "\\U%.8X", (uint32_t)ch);
	else if (ch >= 0x80 && ch <= 0xFFFF)
		return snprintf(buf, sz, "\\u%.4hX", (unsigned short)ch);

	return snprintf(buf, sz, "%c", (char)ch);
}

KS_DECLARE(int) ks_u8_escape(char *buf, int sz, char *src, int escape_quotes)
{
	int c=0, i=0, amt;

	while (src[i] && c < sz) {
		if (escape_quotes && src[i] == '"') {
			amt = snprintf(buf, sz - c, "\\\"");
			i++;
		}
		else {
			amt = ks_u8_escape_wchar(buf, sz - c, ks_u8_nextchar(src, &i));
		}
		c += amt;
		buf += amt;
	}
	if (c < sz)
		*buf = '\0';
	return c;
}

KS_DECLARE(char *) ks_u8_strchr(char *s, uint32_t ch, int *charn)
{
	int i = 0, lasti=0;
	uint32_t c;

	*charn = 0;
	while (s[i]) {
		c = ks_u8_nextchar(s, &i);
		if (c == ch) {
			return &s[lasti];
		}
		lasti = i;
		(*charn)++;
	}
	return NULL;
}

KS_DECLARE(char *) ks_u8_memchr(char *s, uint32_t ch, size_t sz, int *charn)
{
	int i = 0, lasti=0;
	uint32_t c;
	int csz;

	*charn = 0;
	while (i < (int)sz) {
		c = csz = 0;
		do {
			c <<= 6;
			c += (unsigned char)s[i++];
			csz++;
		} while (i < (int)sz && !isutf(s[i]));
		c -= offsetsFromUTF8[csz-1];

		if (c == ch) {
			return &s[lasti];
		}
		lasti = i;
		(*charn)++;
	}
	return NULL;
}

KS_DECLARE(int) ks_u8_is_locale_utf8(char *locale)
{
	/* this code based on libutf8 */
	const char* cp = locale;

	for (; *cp != '\0' && *cp != '@' && *cp != '+' && *cp != ','; cp++) {
		if (*cp == '.') {
			const char* encoding = ++cp;
			for (; *cp != '\0' && *cp != '@' && *cp != '+' && *cp != ','; cp++)
				;
			if ((cp-encoding == 5 && !strncmp(encoding, "UTF-8", 5))
					|| (cp-encoding == 4 && !strncmp(encoding, "utf8", 4)))
				return 1; /* it's UTF-8 */
			break;
		}
	}
	return 0;
}



/* reads the next utf-8 sequence out of a string, updating an index */
KS_DECLARE(uint32_t) ks_u8_get_char(char *s, int *i)
{
	uint32_t ch = 0;
	int sz = 0;

	do {
		ch <<= 6;
		ch += (unsigned char)s[(*i)++];
		sz++;
	} while (s[*i] && !isutf(s[*i]));

	ch -= offsetsFromUTF8[sz-1];

	return ch;
}
